Little is really known about Dewi or St David (6th Century), and we must rely for our information on a biography written five hundred years after his death by Rhygyfarch (1056?-99) of Llanbadarn Fawr. He spent his early life in Ceredigion, and it was there at Hen Fynyw ( a few miles south of Aberaeron) that he received part of his education. It was at Hen Fynyw that Dewi also established his first missionary centre as he evangelised in south-west Wales with the aid of his followers, Aidan, Eiludd and Yswael.
     In time Dewi established his own monastic community at Glyn Rhosyn (where St Davids stands today in Pembrokeshire) and became abbot-bishop. The community lived a very simple life. Dewi himself was known outside the community as one of the aquati (watermen), that is someone who drank water rather than wine and ate fish rather than flesh. When not at prayer or in services the monks spent their time working hard on the land. They used the fruits of their labour to feed the poor and needy. But Dewi's main work, as was that of many members of the community, was to lead preaching crusades in South Wales to spread the gospel message.
     As a preacher Dewi faced challenged from outside the church as well as from within it. He encountered the challenge of paganism as he established his community at Glyn Rhosyn in the face of the opposition of Baia's people and their human sacrifice. He faced heresy in the church at a dramatic synod in Llanddewibrefi (in Ceredigion) where he had refuted the false teachings of Pelagius' followers. There, so that the crowds could hear him clearly, the ground rose miraculously beneath his feet so that all were convinced of the false doctrines of Pelagius' followers and rejected heresy.